Organic electroluminescence displays using organic electroluminescence elements (hereinafter, referred to as organic EL elements) are well-known as image display devices using current-driven light-emitting elements. Due to such advantages as excellent viewing angle characteristics and low power consumption, such organic EL displays have gained much attention as candidates for next-generation flat panel displays (FPDs).
Organic EL elements included in pixels are normally arranged in a matrix shape. For example, in an organic EL display device referred to as an active-matrix organic EL display, a thin film transistor (TFT) is provided in each crosspoint between scanning lines and data lines, and a holding capacitance element (condenser) and the gate of a drive transistor is connected to the TFT. The TFT is turned on through a selected scanning line so as to input a data signal from a data line to the drive transistor and the holding capacitance element, and a light emission timing for an organic EL element is controlled by such drive transistor and the held capacitance element. With the configuration of the pixel drive circuit, in the active-matrix organic EL display, it is possible to cause the organic EL element to emit light until a subsequent scan (selection), and thus a reduction in display luminance is not incurred even when the duty ratio increases. However, in the active-matrix organic EL display, a manufacturing process which requires microfabrication when a structure of a pixel is finer and thinner or when the number of pixels is greater, an electrical defect such as a short circuit and a release of the organic EL element occurs.
Patent Literature 1 discloses a technique of detecting a defective pixel arising in the organic EL element in the manufacturing process of the organic EL display device. In Patent Literature 1, in an inspection device which includes a unit for applying a reverse bias voltage to organic EL elements, a unit for imaging a light leakage state from the organic EL elements under a completely light-shielding condition, and a unit for inspecting the light leakage, light leakage that is greater than or equal to a predetermined luminance is detected from the image. The technique makes it possible to detect a potentially defective portion of the organic EL element in a short time and to determine whether or not the whole of the organic EL element is a good product, and the inspection device cam be used as an inspection device for mass production.